Climbers generally use clean protection devices for two distinct purposes. First, a clean protection device may be used as a form of safety protection for protecting a climber in the event of a fall and second, a clean protection device may intentionally be used to artificially support a climber's weight. Clean protection devices cam or wedge into a crack, hole, gap, orifice, taper, or recess in order to support an outward force. The area or surface within which the clean protection device supports the outward force is considered the protection surface. The protection surface can consist of natural materials such as rock or may consist of artificial materials such as concrete.
Clean protection devices are generally divided into active and passive categories. Passive protection devices include a single object, which contacts the protection surface to support an outward force. For example, a wedge is a passive protection device because it has a single head with a fixed shape. There are numerous types of passive protection devices including nuts, hexes, tri-cams, wedges, rocks, and chocks. Active protection devices include at least two movable objects that can move relative to one another to create a variety of shapes. For example, a slidable chock or slider nut is considered an active protection device because it includes two wedges that move relative to one another to wedge into various shaped crevices. When the two wedges of the slider nut are positioned adjacent to one another, the overall width of the protection device is significantly larger than if the two wedges are positioned on top of one another. The two wedges must make contact with the protection surface in order to actively wedge the device within the protection surface. A further subset of active protection devices is camming devices. These devices translate rotational displacement into linear displacement. Therefore, a slider chock would not be an active camming device because the two wedges simply slide relative to one another and do not rotate. Camming devices include two, three, and four cam lobe devices. The cam lobes on an active camming device are generally spring biased into an expanded position and are able to rotate or pivot about an axle to retract. In operation, at least one cam lobe on either side of the unit must make contact with the protection surface for the device to be able to actively support an outward force. Some active protection devices can also be used passively to support outward forces as well.
Active protection devices are generally preferable to passive protection devices because of their ability to cam into a variety of features. For example, a standard four-cam unit has a particular camming range that allows it to cam into features within a particular size range. The two most common connection systems used in three and four cam units are single stem and double stem systems. Double stem systems include a U-shaped cable that attaches independently to two cable terminals on either end of the head of the protection device. The clip-in point of a double stem system is simply the bottom of the U-shaped cable. Single stem systems include a single cable that is attached to a single cable terminal located at the center of the head of the protection device. The single stem system generally includes some form of clip-in loop attached to the single cable. Single stem connection systems are generally preferable for larger cams because they are less likely to obstruct particular camming placements.
Small camming devices provide protection and/or support from a small protection surface. For most applications, small camming devices must support the same outward forces as larger camming devices. Therefore, in order to provide reliable protection, small camming devices should maximize the camming surface, which contacts the protection surface. This objective becomes more difficult the smaller the protection surface within which the device is designed to accommodate. For example, a camming device that is designed to fit into cracks between 0.1 and 0.2 inches should maximize the camming surfaces of the camming device more so than a camming device that is designed to fit into cracks between 1 and 2 inches. In addition, small camming devices are more likely to pop out of the protection surface from axle bending, inverted cam lobes, or uneven lateral stem bending. Therefore, small camming devices should minimize these affects to ensure reliable placements.